MS36-P03 The dimeric nature of the Re(I) complexes of the thiosemicarbazonate derived of 4-(dimethylamino)benzaldehydeDimeric thiosemicarbazonate complexes [Re2(CO)6(L)2] (see Figure 1) are often isolated from solutions of the corresponding mononuclear rhenium(I) complexes, [ReX(CO)3(HL)], containing the protonated species of those bidentated ligands . The deprotonation of the HL ligand and the labilization of the halogen in adduct produces the dimerization of the rhenium complexes by linking the sulfur atom of a neighboring molecule at the position previously occupied by the halogen atom. The Re–S bond to the sulfur atom belonging to the chelating system of the neighboring rhenium atom is larger (around 0.1 Å) than its own chelate.
When basic media is used to remove the halide group, the dinuclear complex is usually formed in stoichiometric amounts. The stability of thiosemicarbazonate specie depends also of ligand nature, so that the thiosemicarbazones derivated from aldehyde give the dimer more easily than those derived from ketones.
Recently, we had tried the synthesis of rhenium(I) complexes of the thiosemicarbazone derived of 4-(dimethylamino)benzaldehyde and we have observed the systematic formation of the dinuclear complex as crystal from solutions of the monomer in several solvents and at different temperatures.
In addition, we have isolated two different compounds depending of the ligands disposition respect to the Re2S2 diamond: the centrosymmetric arrangement (Figure 1 left) and the dissymmetric arrangement (Figure 1 right). Both dimers were able to isolated as separated single crystals and also as a co-crystal.
In the present work, we study the structural differences between both kind of structures and we describe the possible factors determining the formation of one or other symmetric disposition.
Acknowledgements: Financial support from Ministry of Economy, Industry and Competitiveness (Spain) and European Regional Development Fund (EU) (CTQ2015-71211-REDT and CTQ2015-7091-R) is gratefully acknowledged.
 A. Nuñez-Montenegro, R. Carballo, U. Abram, E.M. Vázquez-López. Polyhedron 65 (2013) 221-228.Keywords: Dimer, thiosemicarbazone, crystal